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Abstract

Direct observation of eruptive activity and related measurements are limited to above the vent and correlations to the source conditions remain challenging. While interpretation of data to infer source conditions relies critically on high-quality data, measurements are commonly conducted at distances safe from the inherent dangers linked to volcanic explosions adding a degree of uncertainty due to enhanced signal path effects. Here, we present custom-built sensors designed to acquire data at high proximity (within 10s of meters) to volcanic vents where direct access would otherwise represent an intolerable risk. These sensors can be deployed by uncrewed aerial vehicles at the desired location. They are equipped with an environmental sensor capable of measuring temperature, relative humidity and barometric pressure, a microphone (6 Hz-20 kHz) to reconstruct the acoustic pressure and an electrical resonant circuit to detect electrical signals in the 500 kHz frequency band. The data is recorded to a ring-buffer capable of storing ~ 38 s of data that can be downloaded after individual explosions. Communication and data transfer is achieved through a LoRa (long range) radio link between the sensor platform and the base station. We tested the feasibility of near-vent deployment at Stromboli, volcano, Italy during two field campaigns in September 2018 and May 2019. During the second campaign we deployed 13 sensors at distances between 15 and 354 m and recorded 47 events. This dataset confirmed the influence of near vent topography on the propagation of acoustic signals and electrical activity in low magnitude explosive activity.